Optical fiber system and method for wellhole sensing of magnetic permeability using diffraction effect of faraday rotator
First Claim
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1. A system for locating magnetic permeability anomalies in wellhole piping and tubing installed within a borehole, said system comprising:
- a source of light located outside a well;
a first optical fiber operable to extend into a wellhole connected to said source of light;
an optical depolarizer in line with the said first optical fiber and located between the well hole and the source of light;
an optical coupler or optical circulator in line with the said first optical fiber located between the optical polarizer and the well hole;
a second optical fiber connected to the said optical coupler or optical circulator;
a signal detector and analyzer connected to said second optical fiber; and
a sensor assembly connected downhole to said first optical fiber, including;
magnets oriented to create a magnetic field within the vicinity of said sensor,an optical collimator attached to said first optical fiber,a Faraday crystal positioned downstream of said optical collimator,an optical reflecting device positioned downstream of said Faraday crystal capable for redirecting the light back through said first optical fiber and, ultimately, to the said signal detector and analyzer located at the well surface, wherein said sensor assembly is operable to experience light insertion losses as a function of perturbations in magnetic fields near said sensor resulting from the masses of downhole tubing adjacent to the sensor assembly.
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Abstract
Systems and methods for optically determining casing collar and/or corrosion locations within boreholes, using the diffraction effect of Faraday crystals through which depolarized continuous light is transmitted within optical fibers.
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Citations
11 Claims
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1. A system for locating magnetic permeability anomalies in wellhole piping and tubing installed within a borehole, said system comprising:
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a source of light located outside a well; a first optical fiber operable to extend into a wellhole connected to said source of light; an optical depolarizer in line with the said first optical fiber and located between the well hole and the source of light; an optical coupler or optical circulator in line with the said first optical fiber located between the optical polarizer and the well hole; a second optical fiber connected to the said optical coupler or optical circulator; a signal detector and analyzer connected to said second optical fiber; and a sensor assembly connected downhole to said first optical fiber, including; magnets oriented to create a magnetic field within the vicinity of said sensor, an optical collimator attached to said first optical fiber, a Faraday crystal positioned downstream of said optical collimator, an optical reflecting device positioned downstream of said Faraday crystal capable for redirecting the light back through said first optical fiber and, ultimately, to the said signal detector and analyzer located at the well surface, wherein said sensor assembly is operable to experience light insertion losses as a function of perturbations in magnetic fields near said sensor resulting from the masses of downhole tubing adjacent to the sensor assembly. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for locating magnetic permeability anomalies in wellhole tubing installed within a borehole, said method comprising the steps of:
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providing a source of light located outside a well; depolarizing light from said source of light; transmitting said depolarized light through an optical fiber into a wellhole to a sensor; creating a magnetic field in the vicinity of said sensor; collimating the depolarized light passing through said sensor; positioning said sensor within said wellhole tubing; moving said sensor in proximity to the wellhole casing such that the mass of the wellhole casing affects the magnetic lines of flux within the Faraday crystal and, in turn, affects the insertion loses of the collimated and depolarized light traversing the Faraday crystal; reflecting light which has traversed the Faraday crystal back to the optical fiber for transport to the surface of the well; and detecting and analyzing said reflected light for insertion losses to determine magnetic permeability anomalies within the wellhole tubing. - View Dependent Claims (8, 9, 10, 11)
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Specification